For your graphics card, you will get a choice of the proprietary driver from the manufacturer and a free alternative. You have to either restart the display server (log out and back in) or restart the system entirely (recommended).

For 12.04 and below

The internal name of the "additional drivers" program is jockey-gtk. There's a console version with the same functionality called jockey-text in the eponymous package. It should be installed by default.

You should be able to use

jockey-text -l

to list the available drivers and something like

jockey-text -e xorg:nvidia-185

to install one of the options listed. You should select the most appropriate driver listed.